Gates SA-39 Filament power question.

[andre tchmil]

Looking at the SA-38, SA-39 schematics, I wonder why there are 3 filament voltage sources through T3, T4.
Was this done to keep the main transformer small or for cost reasons ?
I'm asking because I need to convert a 115V version to 230V and was thinking to replace the main transformer and combine the 6,3v  from one source.

 

[emrr]

You see this as a method to reduce filament induced noise interactions in various limiters, especially the GR tubes.  You see rectifier and audio on separate filament taps, even if both are 6v. 

 

[andre tchmil]

Thanks Doug.